If you’ve been with your partner or spouse for decades, you may have noticed that your lives are more intertwined as time goes on. Maybe you anticipate their coffee order after hearing it every morning, or you just know how to cheer them up at the end of a bad day. Now, researchers say that being together with someone for a long time can lead to a fascinating physiological change: Couples heart rates begin to sync.
In a study published in the Journal of Personal and Social Relationships, scientists wanted to investigate how physical proximity to another person over time can affect how people’s bodies co-regulate together. They followed 10 couples who’d been together for 14 to 65 years over a span of two weeks. The members of each pairing wore a heart rate monitor and a small-proximity sensor, which could detect when couples were physically close to each other.
In the end, they discovered that the longer that couples had been together, the more likely they were to have their heart rates sync on a daily basis. In other words, if one member of the household had an increase in heart rate, the other would soon follow and vice versa. These changes would continue whenever they were together throughout the day.
“This suggests a delicate balance. When one partner triggers the other partner, they start a unique couple-level dance that affects their physiology and their patterns throughout the day,” Brian Ogolsky, PhD, lead author and an associate professor at the University of Illinois, explained about the study. “We found each day is a unique context that changes depending on circumstances. Couple interactions, their attitudes, behaviors, whether they’re close to each other or far away, change all the time.”
However, Dr. Ogolsky is quick to point out that there needs to be more research done to see what these dynamics are like on a larger scale and how they affect people’s health. “If we really want to understand the unique patterns of interaction that happen within couples, we need to start focusing our attention on micro processes; the small interaction patterns that accumulate over a day,” he said. “Those tell us about the nature of how couples’ interactions play out from moment to moment.”
Still, it’s interesting to know that you and your partner are more in sync than you even thought — including on a cellular level!
This article originally appeared on our sister site, First for Women.